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Issue 35, 2018

Mechanism suppressing charge recombination at iodine defects in CH3NH3PbI3 by polaron formation

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Abstract

Metal-halide perovskites exhibit high efficiencies in photovoltaic applications and low recombination rates, despite the high concentrations of intrinsic defects. We here study the hole trapping at the negative iodine interstitial, which corresponds to the dominating recombination center in CH3NH3PbI3. We calculate the free energy profile for the hole trapping at 300 K using the Blue Moon technique based on hybrid functional molecular dynamics. We find that the hole trapping is energetically unfavorable and requires overcoming an energy barrier. This behavior stems from the position of the vertical (−/0) transition level of the iodine defect and the formation of a polaron. Our simulations show that the polaron does not interact with the iodine interstitial and hops through the lattice on a sub-picosecond scale. Our results highlight a mechanism by which the low mononuclear (trap-assisted) recombination rates in CH3NH3PbI3 can be explained.

Graphical abstract: Mechanism suppressing charge recombination at iodine defects in CH3NH3PbI3 by polaron formation

Article information


Submitted
05 Jul 2018
Accepted
16 Aug 2018
First published
17 Aug 2018

J. Mater. Chem. A, 2018,6, 16863-16867
Article type
Communication

Mechanism suppressing charge recombination at iodine defects in CH3NH3PbI3 by polaron formation

J. Wiktor, F. Ambrosio and A. Pasquarello, J. Mater. Chem. A, 2018, 6, 16863 DOI: 10.1039/C8TA06466K

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